1. Field of the Invention
The present invention relates to a jet-propulsion personal watercraft (PWC) which ejects water rearward and planes on a water surface as the resulting reaction. More particularly, the present invention relates to a breather device mounted in an engine.
2. Description of the Related Art
In recent years, so-called jet-propulsion personal watercraft have been widely used in leisure, sport, rescue activities, and the like. The jet-propulsion personal watercraft is configured to have a water jet pump that pressurizes and accelerates water sucked from a water intake generally provided on a bottom of a hull and ejects it rearward from an outlet port. Thereby, the personal watercraft is propelled.
In the jet-propulsion personal watercraft, a steering nozzle provided behind the outlet port of the water jet pump is swung either to the right or to the left, to change the ejection direction of the water to the right or to the left, thereby turning the watercraft to the right or to the left.
In recent years, the use of a four-cycle engine in the jet-propulsion personal watercraft has been contemplated.
When the four-cycle engine is mounted in the personal watercraft, there is a need for a breather device because a volume of a crank case varies with reciprocation of pistons.
In the four-cycle engine, an inner space of the crank case communicates with an inner space of a cylinder head of the engine through a cam chain tunnel or the like. The breather device allows the inner space of the cylinder head to communicate with the outside of the engine through a breather pipe. Or, the breather device allows an inner space of the crank case to communicate with the outside of the engine through the breather pipe. The breather device serves to release a pressure in the crank case resulting from the reciprocation of the pistons to the outside of the engine.
When releasing the pressure inside of the crank case to the outside, the breather device functions to prevent leakage of the oil mist, included in the released air (blow-by gas), to the ambient side.
The breather device needs to function so as to prevent the oil flow from the engine to the ambient side even when the watercraft is inverted.
Meanwhile, since the personal watercraft is commonly used on the water and often splashed with water, regular maintenance such as application of oil is necessary for smooth movement of movable mechanical elements of a throttle device provided in an intake pipe or movable mechanical elements of an air-intake port.
The present invention addresses the above-described condition, and an object of the present invention is to provide a personal watercraft capable of preventing oil flow from an oil reservoir to outside even when the watercraft is inverted. Another object of the present invention is to provide a personal watercraft capable of suitably supplying oil from a breather device to movable mechanical elements of a throttle device provided in an intake passage or movable mechanical elements of an air-intake port.
According to the present invention, there is provided a personal watercraft comprising: a four-cycle engine; a water jet pump driven by the engine, the water jet pump pressurizing and accelerating water taken in from outside of the watercraft and ejecting the water from the outlet port to propel the watercraft as a reaction of the ejecting water; a breather pipe configured such that a base end is connected to the engine to communicate with an inside of the engine, an intermediate portion is located lower than the base end, and a tip end is located higher than the base end; and a breather box, wherein the tip end of the breather pipe communicates with the inside of the breather box and the base end of the breather pipe is located lower than the breather box.
In the personal watercraft so constituted, while the watercraft is not moving or cruising under an engine-running condition, air-containing oil (oil mist) flows from the engine toward the breather box above the engine and is liquefied in the breather box. On the other hand, when the watercraft is inverted, the intermediate portion of the breather pipe is located higher than the base end of the breather pipe communicating with the engine. Therefore, flow of the oil from the engine toward the breather box can be prevented.
It is preferable that the base end of the breather pipe is connected to a breather pipe connecting port provided in a cylinder head of the engine.
It is preferable that the breather pipe has a branch portion at a position lower than the base end, and the branch portion communicates with the inside of a crank case of the engine through an oil return pipe. Thereby, the liquefied oil reserved in the breather pipe can be returned to the engine. This is optimal to the engine, including the oil reservoir provided at the bottom of the crank case of the engine.
It is preferable that the breather pipe has a branch portion at a position lower than the base end, and the branch portion communicates with inside of an oil tank for reserving engine oil through an oil return pipe. Thereby, the liquefied oil reserved in the breather pipe can be returned to the oil tank. This is optimal to the engine of a dry sump type in which the oil tank is provided independently of the engine.
According to the present invention, there is further provided a personal watercraft comprising: a four-cycle engine; a water jet pump driven by the engine, the water jet pump pressurizing and accelerating water taken in from outside of the watercraft and ejecting the water from the outlet port to propel the watercraft as a reaction of the ejecting water; an air-intake passage provided for the engine and provided with an air-intake box; a breather box provided in the air-intake passage and including an oil inlet communicating with inside of the engine; a communicating passage through which inside of the breather box communicates with the air-intake passage; and a breather pipe through which the oil inlet of the breather box communicates with inside of the engine.
In the personal watercraft so constituted, while the watercraft is not moving or cruising under the engine-running condition, oil mist can be supplied from the breather box into the air-intake passage through the communicating passage. The breather box may be provided in the air-intake box or at a different position in the intake passage. Also, by providing the air-intake passage over the cylinder head, the length of the air-intake passage can be extended. Consequently, an engine with a good inertia effect for air-intake is attained.
It is preferable that an inlet of the communicating passage is located as high as or lower than the oil inlet. Thereby, even when the watercraft is inverted, it is possible to prevent the oil reserved in the breather box from flowing toward the intake passage.
It is preferable that the breather pipe is configured such that the base end is located lower than the breather box, the tip end communicates with the inside of the breather box and is located higher than the base end, and an intermediate portion is located lower than the base end.
The personal watercraft may further comprise: an oil return port provided in the breather box; a breather return pipe through which the oil return port communicates with an oil reservoir; and a first baffle wall provided between the oil inlet and the inlet of the communicating passage in the breather box, the first baffle wall extending downwardly from a ceiling wall of the breather box, such that a lower end of the baffle wall is located lower than an imaginary line connecting an upper end of the oil inlet to the inlet of the communicating passage so as to form a space allowing the oil inlet and the inlet of the communicating passage to communicate with each other below the lower end of the first baffle wall.
In the personal watercraft so constituted, while the watercraft is not moving or cruising under the engine-running condition, the oil mist flows through the space below the first baffle wall so as to be supplied from the breather box into the air-intake passage through the communicating passage, and the oil liquefied and separated in the breather box can be returned from the oil return port to the oil reservoir. On the other hand, when the watercraft is inverted, the first baffle wall serves to prevent the oil reserved in the breather box from flowing into the air-intake passage.
The personal watercraft may further comprise: a second baffle wall provided between the oil inlet and the inlet of the communicating passage, the second baffle wall extending vertically from a bottom wall of the breather box, such that an upper end of the second baffle wall is located higher than the imaginary line connecting the upper end of the oil inlet to the inlet of the communicating passage so as to form a space allowing the oil inlet and the inlet of the communicating passage to communicate with each other above the upper end of the second baffle wall. With such a constitution, the oil mist flows above the second baffle wall or above the second baffle wall and below the first baffle wall so as to be supplied from the breather box into the air-intake passage. On the other hand, when the watercraft is inverted, the second baffle wall or the first baffle wall and the second baffle wall serve to prevent the oil reserved in the breather box from flowing into the air-intake passage.
It is preferable that the oil return port is located lower than the oil inlet.
It is preferable that a throttle body to control air flow in the air-intake passage is contained in the air-intake box so that part of oil in the breather box is supplied to the throttle body through the communicating passage.
The personal watercraft may further comprise an oil return port provided in the breather box; a breather return pipe through which the oil return port communicates with an oil reservoir; and a porous plate provided inside of the breather box, for permitting flow of oil between the oil inlet and the inlet of the communicating passage. As defined herein, the porous plate includes plates through which communication is made between the oil inlet and the inlet of the communicating passage, such as a mesh plate or a punching plate.
In the personal watercraft so constituted, while the watercraft is not moving or cruising during engine running, the oil mist passes through holes of the porous plate so as to be supplied from the breather box into the intake passage through the communicating passage, and the oil separated in the breather box can be returned from the oil return port into the oil reservoir. On the other hand, when the watercraft is inverted, the oil reserved in the breather box can be effectively prevented from flowing into the intake passage because of the presence of the porous plate. Against the inversion of the watercraft, the porous plate may be configured to have an upper portion having no holes, for the purpose of more effectively preventing the oil flow into the intake passage.
It is preferable that the breather box is integrally provided at a bottom of the air-intake box and the communicating passage is formed in a separating wall that defines the air-intake box and the breather box.
It is preferable that the breather box is integrally provided inside of the air-intake box and the communicating passage is formed in a separating wall that defines the air-intake box and the breather box. This provides a simplified constitution.
It is preferable that the oil return port is located lower than the oil inlet. Thereby, while the watercraft is not moving or cruising during engine running, the oil reserved in the breather box can be quickly returned to the oil reservoir, for example, to the oil tank or oil reserving portion at the lower portion of the crank case, through the breather return pipe.
It is preferable that a throttle body to control air flow in the air-intake passage is contained in the air-intake box so that part of oil in the breather box is supplied to the throttle body through the communicating passage. Thereby, the oil mist can be supplied to the element outside of the throttle body, for example, to a movable mechanical element such as the throttle mechanism, outside of the throttle body, for lubricating the element. As a matter of course, the oil mist can be supplied to the inside of the throttle body through the opening of the throttle body, thereby lubricating the movable mechanical element.
The above and further objects and features of the invention will be more fully be apparent from the following detailed description with accompanying drawings.